#include <iostream>

using namespace std;

//值传递不能改变原参数据
void change(int& a,int&b)//引用可以理解为别名，直接影响原参
{
    int i;
    i = a;
    a = b;
    b = i;
}

int main()
{
    int x,y;

    cout << "original :" ;
    cin >> x >> y;
    change(x,y);
    cout << "changed :" << x << ' ' <<  y << endl;

    return 0;
}
